In a study of an all-oral drug regimen, a majority of volunteers with liver damage due to hepatitis C virus (HCV) infection were cured following a six-month course of therapy that combined an experimental drug, sofosbuvir, with the licensed antiviral drug ribavirin. The results showed that the regimen was highly effective in clearing the virus and well tolerated in a group of patients who historically have had unfavorable prognoses. Scientists from the National Institute of Allergy and Infectious Diseases (NIAID) and the NIH Clinical Center, parts of the National Institutes of Health, led the Phase II trial.